Explosive Air

Have you considered your air compressor as a potential bomb?

If you have not, then you better!

Although air compressors are built to withstand high pressures, and will have all the necessary relief valves to take care of normal occurring overpressures, explosion involving fire propagation is another matter.

How can a fire occur in an air compressor?

In order to understand the phenomenon of explosion, we have to understand the nature of fire, because, after all, an explosion is a very rapid propagation of fire.

A fire will only start whenever three conditions are met - fuel, oxygen and heat.

An air compressor when operating will have a very rich supply of oxygen already in place - pressurized oxygen.

Where do we get the fuel?

If you use oil lubricated air compressors, the lubricating oil can become the source of fuel. It can also be in the form of carbon dust. Carbon is formed when oil is heated to high temperatures.

How is it possible to have high temperatures to ignite the combustible mixture?

There can be a lot of reasons - lack of lubrication due to oil deterioration, reduced lubricating quality of the oil, oil pump mechanism fault, oil filter choked, worn out parts leading to lessen oil pressures, etc. Whenever there is a hotspot sufficient to ignite the combustible mixture an explosion will occur. That is the extreme case.

Let's see what can happen that can lead to that extreme case of an explosion.

All the above reasons for lubrication failure or deterioration will gradually cause the machine to operate poorly, wear out the moving parts, cause oil spills and carry over of the oil in the air passages and increased heat built-up.

Now comes the cooling part. Is there a lack of cooling? If the high temperatures due to rubbing of parts from the above are not cooled down sufficiently, the heat will build up. The intercoolers play a very important role in removing the heat?

There are also many other reasons for the lack of cooling.

When the heat transfer surfaces have been coated by films of scale or carbon it will definitely affect the cooling process. The heating surfaces may have been reduced due to choked passages for the cooling medium in the heat exchanger. The cooling medium itself may be too hot probably due to a fault in another machine like the cooling tower where the heat can be taken away to the atmosphere.

The flow of coolant can sometimes be the culprit. When the cooling pump fails, or the driving belt snaps there will be a lack of coolant flow. One must also find out whether the valves for coolant have been accidentally closed or not.

Very often, the effects build upon one another in a vicious cycle - poor heat transfer leads to more heat that carbonizes more oil which coats the heat transfer surfaces more...which leads to worse heat transfer...

Therefore use oil lubricated air compressors with caution. If your air compressors have been running for a long time, chances are, your air compressor pipelines may have already accumulated a sizable amount of oil carried over together with the air flow during operation.

Does your air compressor work non-stop? Is the inter-cooler or the after-cooler efficient? Is your compressed air hot? These are the questions you have to ask yourself.

The oil film in the pipes turns to carbon with heat. The oxygen-rich and moist atmosphere inside the pipes can turn the oil into acids that can further deteriorate the oil to form other organic compounds, perhaps some highly flammable products.

It just needs a spark or a hot spot to ignite this.

Boom!!

Did I frighten you?

What you need is good preventive maintenance. An air compressor working at peak condition with good cooling, good lubricating pressures, and good lubricant and good parts should give trouble-free performance throughout its lifetime.

Sometimes the compressor may have reached the point of no return - coated coolers leading to high temperatures that lead to more coated cooling surfaces that lead to higher temperatures... In this case it is safer to discard the compressor altogether and obtain an entirely new compressor unit. It could be more economical - and safer!

If you do that, do ensure that preventive maintenance is done regularly to keep the unit at peak operating conditions all the time.

An explosion in an air compressor can have grave consequences. Don't take any chances. Perform regular preventive maintenance or buy a new unit before an explosion occurs.

Until next time…

Locate good air compressors for your garage and workshop here:
Eastwood

Many years of working experience in Marine, Facilities, Construction has given the author material for writing e-books and articles related to engineering, and management.

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Energy Related Terms Explained

Below are some terms you may encounter while researching energy related products, heating and efficiency:

AFUE (annual fuel utilization efficiency): an efficiency rating that measures the efficiency with which gas and other fossil-fuel-burning appliance use their primary fuel source over an entire heating season. It does not take into account the efficiency with which any component of the system, such as a furnace fan motor, uses electricity. AFUE is expressed as a percentage that indicates the average number of Btu worth of heating comfort provided by each Btu worth of fuel consumed by the system. For instance, a gas furnace with an AFUE of 80% would provide 0.8 Btu of heat for every Btu of natural gas it burned.

Air infiltration: the introduction, usually unintentional, of unconditioned outdoor air into a mechanically heated and/or cooled building. Air infiltration can occur through any opening in the home's structure, including seams where walls meet other walls, window or door frames, or chimneys; holes where wires or pipes penetrate walls, floors or ceilings/roofs; and between the loose-fitting meeting rails of double-hung windows or a door bottom and door threshold. It is one of the major causes of unwanted heat gain and loss, and personal discomfort in buildings.

Alternating Current (AC) - An electric current that reverses its direction at regular intervals or cycles; In the U.S. the standard is 120 reversals or 60 cycles per second; typically abbreviated as AC

Amp - short for "ampere" - this measures the amount of electricity moving through a wire. Most household appliances use 15 or 20 amps of power. Amps are what give electricity its "shock."

Biomass Fuel: Any organic (plant or animal) material which is available on a renewable basis, including agricultural crops and agricultural wastes and residues, wood and wood wastes and residues, animal wastes, municipal wastes, and aquatic plants

BTU (British thermal unit): a measurement of the energy in heat. It takes one Btu of heat to warm one pound of water by 1° Fahrenheit. Btu can be used either to define an air conditioner's cooling capacity (i.e., the number of Btu of heat that can be removed by the system) or a furnace's heating capacity (i.e., the number of Btu of heat that can be supplied by the system).

Chemical Energy - Energy stored in a substance and released during a chemical reaction such as burning wood, coal, or oil.

Combustion - Chemical oxidation accompanied by the generation of light and heat.

Conduction is the transfer of heat through solid objects such as glass, dry wall, brick and other building materials. The greater the difference between the outdoor and indoor temperatures, the faster conduction can occur, increasing a building's energy gain or loss.

Convection is the transfer of heat to or from a solid surface via a gas or liquid current. Where home heat loss and gain are concerned, heat convection is caused by air (gas) currents that carry heat from your body, furniture, interior walls and other warm objects to windows, floors, ceilings, exterior walls and other cool surfaces.

Conversion- A number that translates units of one measurement system into corresponding values of another measurement system.

Cord of Firewood: a tightly stacked pile of wood logs measuring 4' x 4' x 8' (128 cubic feet).

Daylighting is the technique of using natural light from windows, skylights and other openings to supplement or replace a building's artificial lighting system. When applied properly, daylighting can reduce lighting costs. When applied improperly, however, it can not only lead to inappropriate light levels but can also raise the building's cooling costs by introducing high levels of solar heat into the interior of the building. Also see SOLAR GAIN to see how sunlight can affect heating costs.

Direct Current - An electric current that flows in only one direction through a circuit, as from a battery. Efficiency is the degree to which a certain action or level of work can be effectively produced for the least expenditure of effort or fuel. BTU of energy consumed (input) x efficiency = BTU output.

Energy: The ability to do work or the ability to move an object. Electrical energy is usually measured in kilowatthours (kWh), while heat energy is usually measured in British thermal units (Btu).

Energy Efficiency - Refers to activities that are aimed at reducing the energy used by substituting technically more advanced equipment, typically without affecting the services provided. Examples include high-efficiency appliances, efficient lighting programs, high-efficiency heating, ventilating and air conditioning (HVAC) systems or control modifications, efficient building design, advanced electric motor drives, and heat recovery systems.

Emission- A discharge or something that is given off; generally used in regard to discharges into the air. Or, releases of gases to the atmosphere from some type of human activity (cooking, driving a car, etc). In the context of global climate change, they consist of greenhouse gases (e.g., the release of carbon dioxide during fuel combustion).

Heat Content - The gross heat content is the number of British thermal units (Btu) produced by the combustion, of a volume of gas under certain with air of the same temperature and pressure as the gas, when the products of combustion are cooled to the initial temperature of gas and air and when the water formed by combustion is condensed to the liquid state.

Kilowatt-hour (kWh): 1000 watts used for one hour - or any combination of energy multiplied by time that is equivalent to that rate of electrical consumption, such as one watt used for 1000 hours, 10 watts used for 100 hours, or 50 watts used for 20 hours. For example, a 100-watt light bulb left on for five hours each day would consume one kWh every two days. Kilowatt-hour is the primary measure on which U.S. electric companies base most customer billing.

Load Estimate is series of studies performed to determine the heating or cooling requirements of your home. An energy load analysis uses information such as the square footage of your home, window and door areas, insulation quality and local climate to determine the heating and cooling capacity needed by your furnace, heat pump or air conditioner.

Mercaptan - An organic chemical compound that has a sulfur like odor that is added to natural gas before distribution to the consumer, to give it a distinct, unpleasant odor (smells like rotten eggs). This serves as a safety device by allowing it to be detected in the atmosphere, in cases where leaks occur.

Methane -A colorless, flammable, odorless hydrocarbon gas (CH4) which is the major component of natural gas. It is also an important source of hydrogen in various industrial processes. Methane is a greenhouse gas.

Operating Cost is the day-to-day cost of operating an appliance, based on energy use.

Payback period is the amount of time it takes to achieve a full return on an investment. For instance, if a high-efficiency direct vent gas fireplace costs $1000 more than a purely decorative fireplace but would save $500 a year in gas usage, the payback period is 2 years.

Propane (C3H8) - A normally gaseous straight-chain hydrocarbon. It is a colorless paraffinic gas that boils at a temperature of -43.67 degrees Fahrenheit. It is extracted from natural gas or refinery gas streams.

Radiation is a method of heat transfer in which heat is transmitted from surface to surface via infrared waves. Radiant heat warms the surfaces it touches without increasing the temperature of the air through which it travels. All warm bodies radiate infrared energy.

R-value is a measurement of a material's ability to resist heat transfer. Insulation products are rated according to the R-value. The higher its R-value, the greater the product's ability to resist heat flow will be.

Solar Gain is the heat that builds up inside a structure as a result of sunlight that enters through transparent or translucent surfaces, such as windows, and is converted to heat after striking other surfaces inside the building.

Space Heating - The use of energy to generate heat for warmth in housing units using space-heating equipment. The equipment could be either the primary or secondary source of heating.

Thermal Energy - The total potential and kinetic energy associated with the random motions of the molecules of a material.

Thermostat - A device that adjusts the amount of heating and cooling produced and/or distributed by automatically responding to the temperature in the environment. Watt: a unit of electric power. The amount of power required by electric appliances is expressed in watts. Watt-hour is a unit of electric energy, equal to one watt used over a period of one hour.

Volt (V) - The volt is the International System of Units (SI) measure of electric potential or electromotive force. A potential of one volt appears across a resistance of one ohm when a current of one ampere flows through that resistance. Reduced to SI base units, 1 V = 1 kg times m2 times s-3 times A-1 (kilogram meter squared per second cubed per ampere).

Voltage - The difference in electrical potential between any two conductors or between a conductor and ground. It is a measure of the electric energy per electron that electrons can acquire and/or give up as they move between the two conductors. This is how electricity gets from the power plant to your house: high-voltage transmission lines carry the electricity under greater pressure to carry it long distances, while lower-voltage power lines serve individual homes and businesses.

*Article contributed by Karen Duke, Victorian Fireplace Shop

Karen Duke is a fireplace, chimney and hearth industry expert of over 25 years in both the retail and service sectors. She is a CSIA Certified Chimney Sweep and has numerous hearth industry certifications. She is the founder and webmaster of http://www.TheFireplaceChannel.com and she is the co-founder and webmaster of http://www.TheVictorianFireplace.com , which is one of the largest online fireplace retailers in the world. She makes her home in Mechanicsville, Virginia. Karen's contact information can be found on either of the above sites.